Contractible test-plug



I (No Model.) 1

M. F. SMITH.

GONTRAUTIBLE TEST PLUG. I No. 499,682. Patented June 13,1893.

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UNITED STATES Pr ce PATENT MORRIS E. SMITH, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR OF ONE- HALF TO THE \VILLIAM CRAlWIP (it SONS SHIP AND ENGINE BUILDING COMPANY, OF PENNSYLVANIA.

CONTRACTIBLE TEST-PLUG.

SPECIFICATION forming part of Letters Patent No. 499,682, dated June 13, 1893.

Application filed April 18, 1892- Serial No. 4529,5133. (N0 model.)

To aZZ whom it may concern.-

Be it known that I, MORRIS F. SMITH, acitizen of the United States, residing at the city of Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented a certain new and useful Contractible Method of Making Test-Plugs for Testing the Accuracy of the Bores of Cannon, of which the following is a specification, reference being had to the accompanying drawings, in which Figure 1, is a plan view of same, partly broken away; Fig. 2, an end view, and Fig. 3, a cross-sectional view on line 000c of Fig. 1.

In the manufacture of cannon it is required that the bore of the implement be made as nearly cylindrical and of as uniform diameter throughout the structure as is possible, and it is required of the constrncters of ordnance by the government inspectors that the accuracy and perfection of same in the above particulars shall be tested and determined. Heretofore this has been accomplished by passing into and through the bore of the cannon a solid cylindrical steel plug hardened and ground, termed a test-plug attached to a suitable handle, whereby to effect the rotation thereof, said cylindrical plug being required to be of a length not less than equal to five times the diameter of the bore, or caliber of the cannon and having a clearance not to exceed one two-thousandth part of an inch as between the diameter of the test-plug and the bore of the cannon, respectively. By reason of such requirement and owing to inevitable imperfections in the metal of which cannon are constructed and to imperfections incident to the boring of same,it frequently happens that test-plugs become wedged in the cannon, and, constructed as they have heretofore been, their removal, when so wedged, is often attended with difficulty and not infrequently results in the ruin of the cannon.

The object of my invention is the produc tion of a test-plug which will serve efficiently to test the bore of cannon, and which, at the same time, can be readily removed therefrom in case of becoming wedged, without injury to it or to the cannon.

Referring to the drawings 1 is the outer shell, which may be made either of hardened steel, brass or other suitable material; 2, is the longitudinal slit or opening in same; 3, is the central tapering shaft or mandrel provided with a threaded hole; 5, is a screw-plug and 6 is the handle of the instrument having, preferably, a roughened surface for convenience in its manipulation and provided with a shoulder 7.

' I prefer constructing the implement in the following manner, namely: For the outer shell I first take a solid cylinder of steel, or other suitable material, and bore a longitudinal tapering hole therethrough, and then split the tube longitudinally by means of a fine saw; then having formed the central tapering shaft or mandrel from steel, or other suitable metal, I draw or drive, the shell or tube upon the central shaft until the shell expands say about three (3) or four (4) one hundredths of an inch in diameter, and abuts against the shoulder of the central shaft. I then draw the parts closely together and secure them firmly by means of the screw plug 5. I then grind down the outside shell or tube until it is a true cylinder of the size, or diameter required. The outer shell is thus made resilient and provided with a narrow, longitudinal opening extending from end to end.

The advantage pertaining to my improved test-plug over those now in use is great and consists in the fact that should the same become wedged or bound in the cannon being tested I can, by removing the screw-plug readily drive out the central shaft which being done the tube or shell surrounding it will contract sufficiently to enable it to be readily removed, and thus the entireimplement can be readily removed from the cannon without injury to the latter.

I am aware that it is not new, in expanding mandrels, to have an outer shell split longitudinally from end to end, a conical plug to expand said outer shell and a nut to secure the two parts together. Such mandrels would not, however, serve for the purpose of testing the bore of a gun, for while the outer shell may be approximately atrue cylinder before expansion, it would not be such a true cylinder after expansion as is necessary for the purpose in view. Furthermore my test plug is not in any sense an expanding test plug, for While the outer shell, in the course of the manufacture of the test plug, is expanded slightly by the insertion of the tapering shaft this is done simply to make the shell resilient so that it may contract sufficiently, when the shaft is removed, to enable the operator to easily drive it out of the bore of the gun under certain conditions. The plug being once made remains in its finished condition and the outer shell retains its resilient quality until under certain adverse circumstances it becomes necessary to drive out the central shaft in order to permit the outer shell to contract by the resilient quality imparted to it in the course of its manufacture.

Having thus described my invention, What I claim, and desire to secure by Letters Patent, is

The method herein described of making a contractible test plug for the bores of guns or cannons, which consists in forminga tube by making a tapering bore in a solid cylinder of metal, splitting the tube longitudinally, expanding the tube and making it resilient, maintaining said tube in its expanded and resilient condition, and finally grinding the outside of the tube until it is a true cylinder of the required diameter, substantially as and for the purpose specified.

In testimony whereof I have hereunto subscribed my name on this 22d day of March, A. D. 1892.

MORRIS F. SMITH;

\Vitnesses:

CHAS. C. COLLIER, WILLIAM CLARK. 

